A unique neural network within the hypothalamus initiates and maintains reproductive function in humans. It accomplishes this task by coordinating the synthesis and pulsatile secretion of a single neuroendocrine decapeptide, gonadotropin-releasing hormone (GnRH), from this neural network. In the last two decades, several genes and pathways that govern GnRH ontogeny have been discovered by studying humans with GnRH deficiency. Several G protein-coupled receptors (GPCRs) and their cognate ligands have been implicated in the neuroendocrine control of human reproduction. However, the knowledge about many of these new genes and pathways are still in the early stages and require further investigation. The overall goal of my research project is to explore the role of th prokineticin system in the neural network that controls human reproductive development and function. The prokineticin signaling system, prokineticin 2 (PROK2) and PROK2 receptor (PROKR2), has recently emerged as a critical regulator of the neuroendocrine control of reproduction in both mice and humans. PROK2 and PROKR2 are highly expressed in the central nervous system and play an important role in olfactory bulb neurogenesis and subsequently in GnRH neuronal migration. Prokineticin 2 also acts as a key circadian output molecule from the suprachiasmatic nucleus and regulates ingestive behavior in animals. Although both human and mouse studies have confirmed and firmly established a key role of the prokineticin pathway in mammalian reproduction, several features of this biology remain puzzling, suggesting a more complex systems biology of this pathway in humans. The objective of this proposal is to clarify the genetic architecture of GnRH deficiency and to investigate the molecular mechanisms through which PROKR2 mutations affect receptor function. My first aim is to define the role of the PROKR2 heterozygous mutations in isolated hypogonadotropic hypogonadism (IHH), testing the hypothesis that heterozygous mutations in PROKR2 in patients with GnRH deficiency are not sufficient to cause the hypogonadotropic hypogonadism phenotype in isolation, but can contribute to the phenotype in association with a second genetic hit. My second aim is to elucidate mechanisms by which mutations in conserved amino acids interfere with PROKR2 function to recognize the functions of these amino acids and domains of this receptor and also to identify proteins connected to intracellular trafficking (chaperones) and degradation pathways of GPCRs. Together, these studies will advance our understanding of the etiology of GnRH deficiency and the role of prokineticin system in this process, and will provide insights into the structure-activity relationships of the PROKR2, with potential implications for GPCR biology in general. This work will expand my research training to encompass both a molecular approach to understanding the mechanisms that cause disease and a translational approach in relating my findings to the phenotypes of patients with disorders of reproductive development and function.